Reference Manual

The Digi Microcontroller Assist™ hardware
ConnectCore® 8X System-on-Module Hardware Reference Manual --
Preliminary
35
Analog to digital converter
Many of the MCA IOs can be configured as Analog to digital channels. The index of the MCA ADC
channels corresponds to the index of the MCA IO. This means that ADC channel 1 corresponds to the
MCA_IO1, ADC channel 2 to the MCA_IO2, and so on.
The result of the ADC conversion for a given input voltage is inversely proportional to the reference
voltage of the ADC. For the MCA ADCs, the reference voltagecorresponds to the VCC_MCA voltage.
(Note that the i.MX 8X ADCs have a different reference voltage.) The MCA ADC provides 12-bit of
resolution with right-justified, unsigned format output. These ADCs are suitable for low-frequency
sampling(under 10 Hz). For higher frequency sampling, Digi recommends the CPU ADC channels. You
can configure the MCA ADC lines to act as an analog window comparator and generate an IRQ
depending on the voltage level in the input. This feature allows applications to be notified of this event
instead of needing to periodically poll the input for its value.
See the MCA software documentation for additional information about how to configure and access
the MCA IRQ lines.
External voltage reference
The MCA_VREF_OUT pin provides an accurate voltage reference of 1.2V that can be used to provide a
reference voltage for sensors and/or analog devices (such as comparators or ADCs).
The MCA_VREF_OUT pin is disabled by default. You must use software to configure the pin for external
voltage reference.
See the MCA software documentation for additional information about how to control the function of
this pin.
Note that the voltage reference continues normal operation in low power modes (suspend and power
off). Therefore, if the voltage reference is enabled during normal operation but is not required for low
power operation, Digi recommends using the software to disable it before entering low power in order
to minimize the power consumption, and re-enable it when resuming normal operation.
External 32KHz clock output
The MCA_CLKOUT32K pin is a 32.768 Hz square wave output that can be used as clock input by
peripherals requiring a low-frequency, high-accuracy clock.